Immune responses involving T lymphocytes are of major importance in determining the fate of organ and tumor allografts as well as the outcome of many viral infections. The specific reactivity of T lymphocytes with alloantigen occurs through antigen-specific receptors. Selective modulation of T lymphocyte immune responses requires selective interference with the interaction between alloantigens and these receptors either during initiation or effector phases of the immune response. The objective of the proposed studies is to characterize some of the properties of T lymphocyte receptors for alloantigens. Different T lymphocyte populations will be studied for their ability to bind alloantigen. Cell hybridization techniques will be used first to obtain homogeneous populations of alloantibody for use as an immunogen to obtain anti-idiotypic antibody and then to obtain homogeneous populations of anti-idiotypic antibody. The anti-idiotypic antibody will be used to define characteristics of idiotype-positive, antigen specific murine T lymphocyte receptors and to determine the biological activities of such receptor-bearing cells. The ultimate goal is to develop more effective means to modulate specific immune responses through selective interference of the interaction between antigen and specific lymphocyte receptors.